The delicate metalic surface of the mirror at the heart of an
astronomical telescope must be renewed periodically.
When a telescope is pointed to the sky, its mirror is necessarily exposed to the
elements. Oxidation and airborn particles such as dust and pollen gradually reduce
the mirror's reflectivity, making the telescope less efficient.

Washing the mirror helps to restore some of the lost reflectivity,
but can do only so much. Renewing the thin metalic coating requires that the mirror be removed
from the telescope, the old coating carefully stripped with acid, and the glass meticulously
cleaned. The mirror is then placed in a chamber under high vaccuum and a new surface
applied by vaporizing metal in the chamber.

The thin layer of aluminum which coats the front surface of
Lick Observatory's Shane 3-meter Reflector is replaced about every three years.
The task of removing, resurfacing, and replacing the six-ton mirror, occupies a crew of more
than half a dozen technicians for four to five days.

These pages record in pictures the latest realuminizing of the 3-meter mirror, begun on
Monday, February 14th, 2000, and completed on Thursday the 17th.